1. Field of the Invention
This invention relates to a high efficiency wavelength up-conversion transparent glass ceramics composition containing rare earth ions, which can be applied to short wavelength solid lasers, full color displays, infrared light detecting sensors, etc. and a process for the production of the same.
2. Description of the Related Art
Lately, the wavelength up-conversion materials utilizing the electronic transition between a plurality of energy levels of rare earth ions have been watched with keen interest because they can be applied to various fields such as blue or green solid lasers, full color displays, infrared light detecting sensors, etc. As a transparent wavelength up-conversion material with a relatively high conversion efficiency, fluoride single crystals and glasses have hitherto been known. However, it is impossible to produce a fluoride single crystal having an optical homogeneity and practically large size on a commercial scale and in an economical manner, since the fluoride single crystal is excellent in conversion efficiency, mechanical strength and chemical stability, but growth of a high quality one is difficult. On the other hand, since the fluoride glass in the form of a fiber is capable of effectively sealing up an excitation light in a fiber core, a visible light fiber laser having the highest infrared conversion efficiency has been obtained at the present time. However, the fluoride glass is inferior to the fluoride single crystal in thermal, mechanical and chemical stability and has problems of durability, reliability, etc. For example, the fluoride glass tends to be deteriorated by erosion with water and when subjected to irradiation by a laser beam with a large power, it is very liable to be damaged. For the preparation of a fluoride glass fiber, furthermore, precise control of the preparation conditions such as temperature, atmosphere, etc. is indispensable, thus resulting in an increase of the production cost.
On the other hand, as a glass having a very high stability, there is known a composition, typical of optical glasses, comprising, as a predominant component, oxides. Ordinary optical glasses containing the so-called glass-forming materials having a very high chemical bonding strength, such as SiO.sub.2, GeO.sub.2, AlO.sub.1.5, BO.sub.1.5, PO.sub.2.5, etc., exhibit high viscosity and are much more excellent in moldability, water resistance, mechanical strength, etc. than fluoride glasses containing ionic bonding compounds. In oxide glasses, however, the emission efficiency from a number of rare earth ion levels is lower by several figures than that of fluorides, and the oxide glasses are not suitable for use as applying devices utilizing emission of rare earth ions, for example, laser materials.
As the wavelength up-conversion material of the prior art, the glass consisting of high quality fluoride meets with a higher production cost and the oxide glass with high stability meets with a lower emission efficiency.